JP3239558B2 - Power withstanding mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antistatic mechanism applied to a primary radiator which is a component of an antenna mounted on a spacecraft such as an artificial satellite and the like, and is a system used for improving the power resistance performance thereof. .

[0002]

2. Description of the Related Art A primary radiator, which is a component of an antenna mounted on a satellite, has conventionally used a coaxial feed system. However, in this system, transmission loss of electromagnetic waves (microwaves) propagating inside the coaxial cable is increased in a high frequency region of several GHz or more, and it is not expected to obtain high transmission power. The waveguide power feeding method has a small transmission loss in a high frequency region of several GHz or more. As a typical primary radiator of a waveguide feeding system, a primary radiator having a structure in which a sub-reflection portion is directly attached to an opening of a feeding waveguide is exemplified.

In order to fix the sub-reflector to the opening of the feeding waveguide, an insulator such as a resin having good radio wave transmission may be used so as not to affect the electric characteristics of the primary radiator. In the structure, electrical conduction cannot be provided between the sub-reflection portion and the power supply waveguide, and a potential difference is generated between the sub-reflection portion and the power supply waveguide, which may cause discharge. In order not to cause a potential difference between the sub-reflection part and the feeding waveguide,
It suffices to maintain conduction between the sub-reflection part and the waveguide feed part. When used, the directional gain and voltage standing wave ratio (VS.
WR: Voltage Standing Wave
(Ration) is greatly deteriorated.

An improvement in these points is disclosed in Japanese Patent Laid-Open No.
-212101. In this method, a conductor for grounding between the sub-reflector and the waveguide feeder is inserted in the center of the primary radiator as a measure to prevent the sub-reflector from being charged, thereby preventing discharge due to a potential difference. . The diameter of the grounding conductor is reduced so that it does not affect the guide wavelength of the waveguide feeder itself when incorporated in the waveguide feeder.

According to this configuration, it is possible to secure electrical conduction between the sub-reflection section and the waveguide feed section, and it is possible to operate in a circularly polarized wave which does not significantly affect the electrical characteristics of the primary radiator. Become.

[0006]

However, when power is applied to a primary radiator in which such a grounding conductor is inserted and arranged, a part of the microwave is absorbed by the grounding conductor, and the microwave is absorbed on the surface of the conductor. Heat energy is generated due to the energy loss of the waves.

Generally, heat energy generated on the surface of a conductor moves by convection, radiation, conduction, and the like. However, in the universe, since the inside of the primary radiator is in a vacuum, there is almost no transfer of heat energy by convection.

Further, since the diameter of the grounding conductor provided in the primary radiator is reduced, the thermal resistance in the longitudinal direction of the grounding conductor is increased, and there is almost no transfer of thermal energy due to conduction. As a result, the heat energy generated in the conductor is
Most of them will move by radiation. However, the surface of a metal conductor generally has a small thermal emissivity, so that there is a limit to the transfer of thermal energy. Depending on the power input to the primary radiator, the thermal energy cannot move and the conductor is heated to a high temperature. When the conductor is heated, the conductor expands and relaxes, which affects the electrical characteristics of the primary radiator. Further, when the conductor is heated to a high temperature, there is a risk of disconnection.

A conventional primary radiator provided with a grounding conductor is:
Due to such a thermal problem of the conductor, there is a limit on the operating power.

[0010]

The object of the present invention is to provide an antistatic mechanism in which a conductor for the purpose of grounding the sub-reflector is inserted and arranged at the center of the primary radiator. The problem is solved by covering with a metal having a low resistivity and further covering the metal surface with a dielectric having a high thermal emissivity.

[0011]

FIG. 2 shows the energy balance of the grounding conductor in the antistatic mechanism. Microwave energy 4 propagating inside the feeding waveguide 1 enters the grounding conductor 2,
The energy of the microwave becomes thermal energy 7 as a loss. This heat energy is emitted to the outside by radiation from the conductor surface. In other words, the temperature of the grounding conductor is determined by the energy balance between the thermal energy 7 generated by the loss of microwave energy and the thermal energy 5 emitted by the thermal radiation.

The relationship is shown in the following equation.

E ² √ρ = αε (T ⁴ −T ₀ ⁴ ) where E ² is the energy of the microwave incident on the conductor,
ρ is the electrical resistivity of the conductor, ε is the thermal emissivity of the conductor, α is the proportionality factor, T is the absolute temperature of the conductor, and T ₀ is the absolute temperature of the feeding waveguide. Here, ε is a value when the conductor is sufficiently smaller than an object such as a power supply waveguide surrounding the conductor.

The right side corresponds to the thermal energy generated by the incident microwave due to the electrical resistivity (ρ) of the conductor, and the left side corresponds to the fourth power of the absolute temperature of the conductor and the power supply waveguide according to Stefan-Boltzmann's law. (T ⁴ −T)
₀ ⁴ ) and the thermal energy radiated in proportion to the thermal emissivity (ε) of the conductor.

As described above, the conductor temperature is the temperature at which the energy balance between the heat energy generated by the incident microwave due to the electrical resistivity (ρ) of the conductor and the radiated heat energy is balanced.

From these relations, in order to lower the rise temperature of the conductor, first, the thermal energy generated by reducing the electrical resistivity (ρ) of the conductor is suppressed. Since microwaves penetrate the surface of the conductor to the skin depth (skin depth), the conductor surface has the electrical resistivity (ρ)
By covering with a metal having a small size, the energy of microwaves entering the conductor can be suppressed.

However, since the metal conductor generally has a low thermal emissivity, the temperature of the conductor does not always decrease. Therefore, in order to increase the effective thermal emissivity of the conductor, the conductor surface is covered with a dielectric having a higher thermal emissivity than the metal conductor. The dielectric is required to transmit microwaves sufficiently and to have a negligible amount of heat energy generated as a loss on the dielectric as compared with the heat energy generated by the conductor for grounding.

Therefore, as shown in FIG. 1, the surface of the conductor for grounding is covered with a metal 6 having a small electric resistivity (ρ) of the conductor, and the metal surface is further covered with a dielectric material 3 having a large thermal emissivity. In addition, it is possible to reduce the heat energy 7 generated by the microwave incidence 4 and to radiate the generated heat energy 7 more, thereby keeping the temperature of the conductor low.

By using the above mechanism, even when a large power is applied to the primary radiator, the temperature rise of the grounding conductor can be suppressed to a low level, so that the power proof performance of the primary radiator can be improved. It becomes possible.

[0020]

This embodiment will be described with reference to FIGS.

FIG. 3 and FIG. 4 show an antenna mounted on a satellite using an antistatic wire and a primary radiator of the antenna according to an embodiment of the present invention.

FIG. 3 is a side view of the satellite antenna including the main reflector 8 and the primary radiator 9. The main reflecting mirror 8 has a special conical shape, reflects circularly polarized waves radiated from the tip of the primary radiator 9, and forms a radiation pattern required for a terrestrial receiving station.

FIG. 4 is a sectional view of the primary radiator 9 shown in FIG. The primary radiator 9 includes a rectangular circular converter 10, a circular polarization generator 11, a horn cap unit 12, and an antistatic unit 1.
6 is comprised. The horn cap portion 12 comprises a straight pipe 15, a cap cover 14, and a sub-reflection portion 13, and the antistatic portion 16 comprises an antistatic wire 17 and a ground plate 18.

The cap cover 14 is a holding member provided for attaching the sub-reflection portion 13 to the straight pipe 15, and is made of a dielectric material such as a glass epoxy resin.

The anti-static wire 17 is connected to the sub-reflection section 13 so that a potential difference does not occur between the sub-reflection section and the feeding waveguide.
From the center to the straight pipe 15 and the circularly polarized wave generator 11
And, it is coupled to the ground plate 18 via the rectangular-circular converter 10.

Since the linearly polarized wave propagates through the inside of the rectangular-circular converter 10, the ground plate 18 is mounted so as to be orthogonal to the linearly polarized plane to reduce the influence of the electric characteristics of the primary radiator 9.

When power is applied to the primary radiator 9, the input microwave is first converted in the rectangular-circular converter 10 from a rectangular waveguide propagation mode to a circular waveguide propagation mode. Next, the linearly polarized wave propagated from the rectangular-circular converter 10 is converted into a circularly polarized wave by the circularly polarized wave generator 11, and propagated to the sub-reflector 13 via the straight pipe 15. The sub-reflector 13 reflects the circularly polarized wave and radiates the reflected light toward the main reflecting mirror 8, thereby forming a radiation pattern required for an antenna on the ground as an antenna.

Next, the antistatic wire 17 installed on the primary radiator 9 will be described.

FIG. 5 is a cross-sectional view of an antistatic wire 17 showing an embodiment of a countermeasure against electric power of the antistatic mechanism according to the present invention. The diameter of the antistatic wire 17 provided in the primary radiator 9 is set to 0.3 mm or less so as not to affect the electrical characteristics. When the antistatic wire 17 is provided on the primary radiator 9, an appropriate tension is applied to the wire so as not to be loosened due to a rise in temperature. Therefore, in this embodiment, the stainless steel wire 19 having a large material strength and a nonmagnetic material is used. Used. However, the antistatic wire 17 need not be limited to a stainless steel wire as long as the material satisfies the above conditions.

However, when the stainless wire 19 is used as the antistatic wire 17 of the primary radiator 9, the stainless wire 19 has a large electric resistivity and a small thermal emissivity. High temperatures easily cause loosening due to elongation. When the stainless wire is slackened due to elongation, the electrical characteristics of the primary radiator deteriorate. Therefore, in this embodiment, the stainless wire 19 is covered with a material such as gold or silver having a smaller electric resistivity (ρ) than the stainless wire 19. This gold or silver thickness requires a Skin Depth of 1 micron or more for a frequency of 8 GHz. The energy of microwaves entering the stainless wire 19 is reduced by these materials having low electric resistivity.

However, materials such as gold and silver can reflect microwaves because of their low electrical resistivity, but their thermal emissivities are extremely low, less than 0.1, so they are actually generated on their own. Thermal energy cannot be transferred by thermal radiation. That is, as a result, the conductor itself including gold or silver stores thermal energy.

Therefore, in order to promote the transfer of thermal energy, the surface of the gold plating 20 is coated with Teflon 2 having a large thermal emissivity.
Covering with a dielectric material such as 1 increases the effective thermal emissivity. Thereby, the heat energy of the conductor itself including gold or silver moves through Teflon, so that the temperature rise of the conductor can be suppressed to a low level. The thickness of the dielectric such as Teflon 21 is adjusted according to the thermal emissivity.

It is needless to say that the dielectric such as Teflon 21 is required to sufficiently transmit microwaves supplied to the primary radiator 9. Teflon 21 is also a material with small outgassing, and is suitable for use in space.

As described above, the thermal energy generated by the incidence of the microwave can be reduced and the generated thermal energy can be radiated more, so that the temperature of the grounding conductor 2 can be kept low. That is, the primary radiator 9
, The temperature rise of the grounding conductor 2 can be suppressed low.

In this embodiment, the conductor is made of stainless steel, and gold or silver is used as a material for covering the stainless steel, and Teflon is used as a material for covering the gold or silver as an example. Since reliability during operation is required, it is significant to select these highly reliable materials to form an antistatic wire.

Although the present embodiment shows an antistatic wire, it goes without saying that a similar effect can be obtained if the inside of the waveguide or the inner wall is affected by microwaves.

It is needless to say that the present embodiment is not limited to the space and has the same effect in a vacuum state.

[0038]

According to the present invention, an antistatic wire 1 is provided.
7 can be kept small. This also allows greater power to be applied to the primary radiator 9,
The power durability of the antenna is improved.

[Brief description of the drawings]

FIG. 1 is a heat balance diagram in a case where a grounding conductor 2 is used after taking measures against electric power.

FIG. 2 is a heat balance diagram when a grounding conductor 2 is used alone for an antistatic mechanism.

FIG. 3 is a side view of a satellite-mounted antenna.

4 is a sectional view of the primary radiator 9. FIG.

FIG. 5 is a sectional view of an antistatic wire 17 according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Waveguide for electric power feeding, 2 ... Conductor for grounding, 3 ... Dielectric whose thermal emissivity is larger than the metal surface, 4 ... Energy of microwave incident on the conductor for grounding, 5 ... From conductor for grounding Radiated heat energy, 6: metal having lower electrical resistivity than grounding conductor, 7: heat energy generated by microwave loss, 8: main reflecting mirror, 9: primary radiator, 10 ...
Rectangular circular converter, 11 circular polarization generator, 12 horn cap unit, 13 auxiliary reflection unit, 14 cap cover, 1
5: Straight pipe, 16: Antistatic part, 17: Antistatic wire, 18: Ground plate, 19: Stainless steel wire, 20: Gold plating, 21: Teflon

Continuing on the front page (72) Inventor Yasuwara Harada 216 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Information and Communications Division (72) Inventor Akio Tachibana 216 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa (56) References JP-A-57-78115 (JP, A) JP-A-1-212101 (JP, A) JP-A-59-161008 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) H01Q 19/13 H01Q 15/14-15/22 H01B ⁷ /00-7/02

Claims (5)

(57) [Claims] 1. A primary radiator of the antistatic mechanism of Satellite Antenna with antistatic wire was inserted arrangement for grounding the sub-reflecting portion to the central portion, antistatic wire and the conductor, the conductor surface A power withstanding mechanism, comprising: a covering metal; and a dielectric covering the metal. 2. The power withstanding mechanism according to claim 1, wherein said conductor is made of stainless steel. 3. The power withstanding mechanism according to claim 1, wherein the metal is gold or silver. 4. The power withstanding mechanism according to claim 1, wherein the dielectric is Teflon (registered trademark). 5. An antistatic mechanism for an antenna mounted on a satellite in which an antistatic wire for grounding a sub-reflector is inserted at the center of the primary radiator, wherein the antistatic wire is a conductor and a primary radiator. A power-resistant mechanism comprising a material having a high thermal emissivity capable of substantially transmitting radio waves propagating inside the primary radiator, which covers a conductor surface to reflect electromagnetic waves propagating inside.